Chemoselective reduction of α,β-unsaturated carbonyl compounds with UiO-66 materials

• A stable and recyclable UiO-66 supported Ag nanoparticle catalyst was developed.
• Ag/UiO-66 catalysed H2-driven chemoselective reduction of cinnamaldehyde to allylic alcohol.
• CUS Zr-sites in UiO-66 catalyse the MPV-reduction of cinnamaldehyde in isopropanol.
• The substrate scope of the MPV-reduction was extended to citral and carvone.

Allylic alcohols, important intermediates in fine chemical industry, are typically obtained through chemoselective hydrogenation of α,β-unsaturated aldehydes. Here we show that UiO-66, a zirconium-based metal–organic framework can be used in the chemoselective hydrogenation of cinnamaldehyde, both under high hydrogen pressure as silver nanoparticle support, and as transfer hydrogenation catalyst in the Meerwein–Ponndorf–Verley (MPV) reduction. A recyclable 10 wt% Ag/UiO-66 catalyst reached complete conversion after 6 h and 50 bar of H2 with 66% selectivity for cinnamyl alcohol in the inert solvent N,N-dimethylacetamide (DMA). Pure UiO-66 as MPV catalyst with isopropanol reached complete conversion with >90% selectivity after 24 h at 120 °C. The substrate scope was extended to citral and carvone, two α,β-unsaturated carbonyl compounds that are harder to reduce selectively. Introduction of a NO2-functional group into the UiO-66 linker to increase the Lewis acidity was clearly beneficial for the conversion of carvone.

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